A typical musical instrument of the acoustic percussion family such as, for example, a xylophone or a marimba is provided with tuned bars in keyboard arrangement and gradated in length to provide a chromatic scale of three or four octaves. When a performer strikes the bars with rubber-tipped mallets, the bars vibrate at the respective natural frequencies which cause the bars to produce respective tones so as to make a fine melody.
However, in an electronic percussion instrument corresponding to the xylophone or the marimba, tones are produced by a tone generation unit incorporated therein so that bars are only expected to detect strikings with the the mallets. Then, a typical bar incorporated in the electronic percussion instrument forms an electric switch for detecting the striking with the mallet and the structure thereof is illustrated in FIG. 1.
Referring to FIG. 1 of the drawings, there is shown a typical example of the bar incorporated in the electronic percussion instrument. The bar comprises a supporting member 1 of an insulating material and a conductive wirings 2 which are patterned on the upper surface of the supporting member 1. On the upper surface of the supporting member 1 is further mounted a mechanical switch 3 which has an actuator 4 movable into or out of a casing 5. Though not shown in the drawings, the actuator 4 causes a pair of contacts (not shown) to be closed or open depending upon the movement thereof. The contacts are coupled to a pair of conductive wirings 2, respectively, then the switch 3 produces an electric signal when being depressed. The conductive wirings are sandwiched between the supporting member 1 and a covering plate 6 which has a step portion forming a hollow space. A top plate 7 is located in the hollow space and contacted to the actuator 4 of the switch 3. The peripheral portion of the top plate 7 is supported by the step portion of the covering plate 6 under a suitable force exerted thereon so that the top plate 7 depresses the actuator 4 for causing the switch 3 to produce the electric signal but does not crust the switch 3. When a performer strikes the bar illustrated in FIG. 1 with a rubber-tipped mallet 8, the top plate 7 moves downwardly and depresses the actuator 4, then the switch 3 produces the electric signal representing the strike of the mallet 8.
Another example of bar incorporated in an electronic percussion system is illustrated in FIG. 2. The bar illustrated in FIG. 2 comprises a supporting member 11 formed with a stepped portion forming a cavity, a top plate 12 located in the cavity, and a resilient film 13 intervening between the supporting member 11 and the top plate 12. In a space formed between the supporting member 11 and the top plate 12 is provided a piezo-electric member 14 attached to the top plate 12. The bar thus arranged is operative to produce an electric signal when the piezo-electric member 14 is caused to be exerted with pressure due to the movement of the top plate 12.
The prior-art bars illustrated in FIGS. 1 and 2 are operative to produce the electric signals representing the strikes of the mallets, respectively, based on the forces acting on the top plates 7 and 12. However, a problem has been encountered in the prior-art bars in that the electric signals could not reflect a difference in rendition. Namely, there are several renditions for percussion performance such as, for example, tremolo or glissando. When a performer rapidly slides the mallet over the bars of the electronic percussion system, each of the bars produces the electric signal having a certain waveform. However, the signal due to sliding the mallet is similar in waveform to that produced upon simply striking with the mallet in so far as time periods of depression are equal to each other.
It is therefore an important object of the present invention to provide a bar suitable for an electronic percussion system.
It is also an important object of the present invention to provide a bar capable of producing electric signals reflecting a difference in rendition.